DESCRIPTION: Children with mental retardation are four to five times as likely to have psychiatric disorders as are non-disabled children (Pfeiffer & Baker, 1994) yet study of this phenomenon in children has been limited. It is unclear whether the primary risk for dual diagnosis is a function of factors that are endogenous or exogenous. Nevertheless, it seems likely that family functioning may play a critical role in the eventual emergence of psychiatric disorder, particularly through its influence on developing self-regulatory skills. There are five primary aims to the proposed research: 1) to identify family processes that contribute to the development of behavior disorders in young children with mental retardation; 2) to identify family processes that promote social, behavioral, and emotional competence in these children; 33) to identify factors related to the development of behavior and emotion regulation in young children with mental retardation; 4) to determine the contribution of children's developmental state (particularly regulatory and cognitive abilities) to the emergence of comorbid behavior disorders, and 5) to compare these processes to those of normally developing children and their families. A dual-site prospective study of 120 families of young children (from age 3 to 5 years) with developmental delays is proposed. A comparison sample of CA-matched normally developing children and their families will also participate (N=120). At 36, 48, and 60 months extensive interview data will be obtained, addressing family functioning. Naturalistic home observations, detailing family interaction patterns and quality of relationships, will be conducted when children are 36, 42, 48, and 54 months of age. Further, structured laboratory assessments of parent-child interaction and children's self-regulatory behaviors will be conducted at both 36 and 48 months. Finally, at 60 months of child age, assessments of children's psychiatric status, developmental abilities, and self-regulatory skills will be accomplished. This research will detail the complex interrelations between children's developmental status, family relationships, and the emergence of dual diagnosis conditions during early childhood.